The proposed research extends our efforts in the following areas of primate developmental psychobiology: (1) The behavioral/hormonal consequences of different separation conditions in mother-infant dyads. Response to separation in mothers and infants is particularly relevant to our view of mother-infant relationships in terms of the ontogeny of coping. (2) The behavior of the infant following separation under conditions when the pituitary-adrenal response has been pharmacologically altered prior to separation. We have proposed that distress vocalization is an instrumental behavior that leads to mother-infant reunion and, therefore, is a learned response. In traditional learning paradigms, ACTH tends to delay extinction, while prolonged exposure to cortisol facilitates extinction. Early phases of the separation response may be predominantly influenced by ACTH, which facilitates the continuation of calling, whereas under prolonged separation, high levels of cortisol would tend to diminish the rate of vocalization by causing more rapid extinction. To test these hypotheses, separation behavior will be investigated while selectively blocking pituitary-adrenal activity by the administration of endogenous hormones. (3) The ontogeny of fear responses in infant squirrel monkeys. (4) The development of a nonhuman primate model for assessing effects of psychologically-induced stress on immune responses. (5) The effects of the presence of social partners during stress and the influence of social partners in modulating the stress response. Particular emphasis will be placed on the development of skills within the field of immunology; on extending our research into both primate and human models of psychoimmunology; and to begin to develop a program of human psychobiology. This last program will focus on the effects of prenatal stress (measured by questionnaires or event diaries) both on the mothers' neuroendocrine responses and on pregnancy risk, birth difficulties, and the subsequent behavioral and endocrine responsivity of the developing infant. To facilitate the development of the human psychobiology program, this applicant is currently involved in planning a large cohort study to be carried out collaboratively between this laboratory, the Kinsey Institute, and the Hvidovre Hospital in Copenhagen.